Efficacy of primidone in dogs with seizures unresponsive to phenobarbital

Fifteen epileptic dogs had been treated with high dosages of phenobarbital but had not achieved adequate control of their seizures. Their treatment was switched to comparable and higher dosages of primidone. Serum concentrations of phenobarbital were measured in all dogs before and after primidone therapy was initiated, to ensure that the primidone dosage achieved comparable or higher values when derived from primidone. Only one dog experienced improvement in seizure control, indicating that there is no advantage to the use of primidone over the use of phenobarbital for the control of seizures in most dogs.